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    <title>Document</title>
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    <script>
        // undefined
        // var x;
        // alert(x)
        // 字符
        var str1 = "hello world";
        var str2 = 'hello world';
        console.log(str1)
        console.log(str2)
        // var str3 = "hello "world';
        var str4 = '小明说："小红很漂亮"';
        console.log(str4);
        var str = "Java";
        //  JS中先运算等号右边的语句
        str = str + "Script";// 字符串中+号是连接的意思 JavaScript
        console.log(str);
        </script>
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